The COVID-19 pandemic is a global public health crisis that has made a substantive contribution to excess global deaths in 2020 and 2021, and set to do so again in 2022. With COVID-19 cases soaring in many regions of the world, the roll-out of COVID-19 vaccines is likely to be the cornerstone in reversing infection rates. It is also apparent that with the rise in new variants of concern, principal among them the B.1.617.2 ‘Delta’ variant, those who have been vaccinated will likely need booster vaccines. This is particularly the case in vulnerable groups, but also in the general population as vaccine-induced immunity has been shown to decay over time. However, rates of vaccine uptake rates are slowing, with vaccine hesitancy among those who remain unvaccinated cited as a major contributor. In the present study, we aimed to examine the key psychological correlates of COVID-19 vaccine intentions and intentions receive a booster vaccine. The study adopted a single-occasion correlational survey design. Participants were US (N = 499) and Australian (N = 522) residents recruited from an online survey panel. Participants completed scaled measures of vaccine hesitancy, risk perceptions, attitudes, subjective norms, and perceptions of control, and intentions with respect to receiving a COVID-19 vaccine. We also measured these constructs in a US sample of previous COVID-19 vaccine recipients (N = 479) with respect to receiving a COVID-19 booster vaccine. Data were analyzed using multi-group path analysis. Results indicated consistent medium-sized effects of attitudes, and small-to-medium sized effects of subjective norms and vaccine hesitancy, on intentions across the three samples. Risk perceptions predicted intentions in the Australia vaccine and US booster vaccine samples only with small effect sizes. Findings support a consistent pattern of beliefs with respect to vaccine and booster vaccine intentions, particularly the role of attitudes, norms, and vaccine hesitancy. Results are expected to contribute to the evidence base of potentially modifiable factors that could be targeted in interventions to promote intentions to get vaccinated, particularly interventions adopting strategies to allay vaccine hesitancy.